In relation to push-button switch members, as a contact member that can elastically move into contact with and move apart from a contact on a circuit board, there is conventionally known a contact member in which a thin metal plate or a plated metal plate is affixed to a silicone rubber. As contact members of other forms, there are also conventionally known a contact member in which holes are opened in a thin metal plate, a contact member in which a wire mesh is affixed to a silicone rubber, and a contact member in which the wire mesh is covered with a different type of metal (refer to Patent Literatures 1 to 4).
FIG. 10A to 10D illustrate plan views and cross-sectional views (10A, 10B, 10C, 10D) of conventionally known contact members. A contact member 50 illustrated in FIG. 10A has a configuration where a metal plate 52 made of nickel, SUS or the like is affixed to one surface of a disc-shaped silicone rubber 51, as illustrated in a cross-sectional view taken along a line P-P. A contact member 60 illustrated in FIG. 10B has a configuration where a metal plate 62 made of nickel, SUS or the like is affixed to one surface of a disc-shaped silicone rubber 61, and a coat layer 63 of gold or the like is provided on a surface of the metal plate 62, as illustrated in a cross-sectional view taken along a line Q-Q. A contact member 70 illustrated in FIG. 10C has a configuration where a mesh (wire mesh) 72 of a metal such as nickel, SUS or the like is affixed to one surface of a disc-shaped silicone rubber 71, as illustrated in a cross-sectional view taken along a line R-R. A contact member 80 illustrated in FIG. 10D has a configuration where a wire mesh 82 coated with gold or the like in advance is affixed to one surface of a disc-shaped silicone rubber 81, as illustrated in a cross-sectional view taken along a line S-S. A coat layer 83 covers almost the whole surface of the wire mesh 82.
The contact members 50, 60 illustrated in FIGS. 10A and 10B, respectively, have a low resistance and a superior electrical conductance. In the contact members 50, 60, however, a surface brought into contact with a contact on a circuit board is flat, resulting in a problem in that the contact between the surface and the contact on the circuit board is easily affected by foreign matters interposed therebetween. To solve this problem, as with the contact members 70, 80 illustrated in FIGS. 10C and 10D, an approach is adopted in which a surface brought into contact with a contact on a circuit board is made up of a wire mesh like the wire meshes 72, 82 to form an irregular surface that can still come into contact with the contact on the circuit board even though foreign matters are interposed therebetween. Additionally, there is also known an approach where a metal plate including holes is used in place of the wire mesh like the wire meshes 72, 82.